Francis samuel tomey



(Specimens.)

P. S. TOMBY.- MANUFACTURE OF THBYRMOMETBR TUBING.

wmvsssas. I I E iJ/ (M7 Maw 1 UNITE STATES FRANCIS SAMUEL TOME Y, OFBIRMINGHAM, ENGLAND.

MANUFACTURE OF I'HER'MOMETER-TUBING.

SPECIFICATION forming part of Letters Patent No. 568,591, datedSeptember 29, 1896. Application filed August 3,1895- SeIial No. 558,109.(Specimens) To all whom it may concern:

Be it known that I, FRANCIS SAMUEL TO- MEY, glass-tube manufacturer, of142 Victoria Road, Aston, Birmingham, in the county of Warwick, England,have invented a new and useful Improvement in the Manufacture ofThermometer-Tubing, of which the following is a full, clear, and exactdescription.

This invention relates to the manufacture of tubing for clinical,chemical, and other thermometers that are intended to have thegraduations and figures of the thermometric scale etched upon the rearof the stem, so as to be visible when viewed through the stem, upon anenamel ground behind the bore. WVith this object in view it has longbeen desired to draw'the tube with a very thin external coating ofenamel applied, preferably, upon a flat surface, which when thethermometer is finished would form the back of the stem and upon whichsurface the scale would be marked by etching through the enamel. Athermometric scale so produced would be practicallyindestructible,since, the divisions and figures being etched through the enamel, thescale would be visible even should all the black filling be removed byacids or by cleaning. It has not, however, been possible to producecommercially and by the ordinary methods of manufacture enameledthermometer-tubing suitable for the purpose of being so etched, owing tothe impossibility of applying a sufficiently thin coating of enamel toso extended a surface as that of what is known in the trade as thepiece. The ordinary method of applying the enamel is to gather therequired quantity onto a pontil and fiatten it, then to warm it again atthe pot-mouth, and while very hot to apply it in the required positionbut experience has heretofore shown that when the enamel has beenflattened thin enough for the desired purpose it has invariably run intocorrugations immediately upon being exposed to the heat preparatory tobeing applied to the required position on the piece, to which it nevercould be applied without air-blisters being left between itself and theflint metal and without such unevenness in thethickness of the coatingof enamel as to cause it to break while being drawn out. Even were itfound possible to apply a sufficiently thin coating of enamel to thepiece and that the piece so coated were drawn out in the form of athermometer-tube,

the thickness of the enamel has un avoidablybeen so variable as torender impossible the proper performance of the etching operation,inasmuch as it is not practically possible to obtain sufficient actionof the acid to produce the required depth of etching on the parts wherethe enamel is thick and yet prevent excessive action of the acid wherethe enamel is thin.

Reference is to be had to the accompanying drawings, in which Figure 1is a cross-sectional View of the piece; and Fig. 2 is a brokenelevation, partly in section, of the furnace containing the enamel-potand illustrating the manner of applying the enamel.

c is the piece, having a bore hand a flat face on which is applied thecoating of enamel designated a.

In Fig. 2, c is the enamel-pot, located upon a suitable support cl andprovided with an open neck 0, disposed toward an opening 6 in the wall 6of the furnace. A scraper s is arranged in the mouth of the enamel-pot,said scraper being beveled to a true knife-edge and is made smooth andpolished after grind- 1n g.

To overcome the difficulties inherent to the above -described usualprocess of making thermometer-tubing, I blow the ball and form the borein the usual way, omitting, however, the enamel. I then cover the ballwith metal to the required thickness and marver it to a cylindricalform. Then, having reheated it, I carefully flatten the back of thepiece a upon a marver or other suitable surface. I then dip the piececarefully into the fluid enamel f, contained in the pot 0, takingespecial care to prevent contact of the enamel with any but just theflattened surface of the piece, and having allowed the enamel to drainoif I carefully draw the fiat surface of the piece over the knife orscraper s (fixed in the mouth 0' of the enamel-pot) before the enamel onthe piece has had time to become chilled in the slightest degree. Allthe superfluous enamel is thus removed from the coated flat side of thepiece, the enamel coating being left in the form of a perfectly flatfilm of absolutely uniform thickness and free from blisters. The pieceis then marvered and heated and drawn out into the form ofthermometer-tubing in the usual way.

It is to be observed that the enamelin which the piece is thus dippedmust be very hot and as fluid as possible and must be of such acomposition that its coefficient of contraction and expansion undervariations of temperature will be the same as that of the flint metal ofwhich the piece is made.

I claim- The hereiu-described method of manufacturing enameled tubingfor thermometers which are to have the scale etched through the enamel,which method consists in form In presence of- JAMES OLEWs, JOsEPI-IBENJAMIN FREEMAN.

